PSQuantifying Facies Attributes of the Caicos Platform*
Paul M. (Mitch) Harris1 and Brigitte M. Vlaswinkel2
Search and Discovery Article #50079 (2008)
Posted August 1, 2008
*Adapted from poster presentation at AAPG Annual Convention, San Antonio, Texas, April 20, 2008. See companion articles, “Trend Metrics of Modern Carbonate Depositional Systems,” Search and Discovery Article #50081 (2008) and “Input for Carbonate Reservoir Models: Trend Metrics of Modern Platforms and Reef Systems,” Search and Discovery Article #50127 (2008).
1Chevron Energy Technology Company, San Ramon, CA 94583 ([email protected])
2Shell International E&P, Rijswijk, 2288 GS, The Netherlands ([email protected])
Spatial heterogeneity is a basic characteristic of carbonate depositional systems. Examining spatial depositional patterns and quantifying the facies attributes (e.g., size, shape, and facies interrelationships) in modern analogs can decrease uncertainty in a geologic model and therefore enhance the model’s utility. In an attempt to gather such valuable data, the attributes for key facies of the Caicos platform are assessed from a Landsat image through facies mapping. Reef-associated facies, including fully aggraded reef, partially aggraded reef, and apron are emphasized due to their importance in many isolated platform reservoirs.
Some key findings are:
1. Platform size and reef abundance are directly related, wherein reef (fully and partially aggraded) and reef apron occupy a smaller percentage of a large platform like Caicos.
2. Reefs seem to be patchier than aprons.
3. Fully aggraded reefs become somewhat wider as their length increases; partially aggraded reefs are discontinuous along their long axis so the relation to reef width is more subtle.
4. Reef width and apron width are directly related.
5. Probabilities can be set for expected dimensions for: reef width (10% probability that reef width > 410 m, 50% probability > 270 m, and 90% probability > 145 m); and apron width (10% probability that apron width > 945 m, 50% probability > 395 m, and 90% probability > 90m).
Modern analogs like Caicos can play an important role as conceptual facies models for characterization of a reservoir, and also in providing facies attribute information to be used as input in building reservoir models
1) Fully aggraded reef
2) Partially aggraded reef
3) Reef apron
5) Shallow platform interior (w or w/o isolated reefs)
6) Intermediate platform interior (w or w/o reefs)
7) Deep platform interior (w or w/o reefs)
8) Forereef/outer platform
9) Land/exposed terrain
Grötsch, Jürgen, and Christophe Mercadier, 1999, Integrated 3-D reservoir modeling based on 3-D seismic: The Tertiary Malampaya and Camago buildups, offshore Palawan, Philippines: AAPG Bulletin, v. 83, p. 1703-1728.